1. Technical Field
The present invention relates, in general, to a fuel cell having a manifold which is able to collect electric current.
2. Description of the Related Art
Generally, a fuel cell is a device in which the chemical energy of a fuel (e.g., hydrogen, LNG, LPG or the like) and air is converted directly into electrical energy and heat by an electrochemical reaction. Unlike existing electricity-generation technology which requires the processes of combusting the fuel, generating steam, driving a turbine, and driving a generator, the fuel cells do not need to perform the combustion process nor do they need a driving device, so that they are a next generation technology which generates energy in high efficiency without inducing environmental problems.
FIG. 1 is a view illustrating the principle of operation of a fuel cell.
Referring to FIG. 1, an anode 1 is supplied with hydrogen (H2) and decomposes it into hydrogen ions (H+) and electrons (e−). The hydrogen ions are delivered to a cathode 3 via an electrolyte 2. Electrons travel through an external circuit to thereby generate an electric current. At the cathode, the hydrogen ions, electrons and oxygen in the air react with each other to produce water. A chemical reaction at the fuel cell 10 can be expressed by the following reaction 1:
                                          Anode            ⁢                                                  ⁢            1            ⁢                          :                        ⁢                                                  ⁢                          H              2                                ->                                    2              ⁢                              H                +                                      +                          2              ⁢                              e                -                                                    ⁢                                  ⁢                                            Cathode              ⁢                                                          ⁢              3              ⁢                              :                            ⁢                                                          ⁢                              1                2                            ⁢                              O                2                                      +                          2              ⁢                              H                +                                      +                          2              ⁢                              e                -                                              ->                                    H              2                        ⁢            O                          ⁢                                  ⁢                                            Total              ⁢                                                          ⁢              Reaction              ⁢                              :                            ⁢                                                          ⁢                              H                2                                      +                                          1                2                            ⁢                              O                2                                              ->                                    H              2                        ⁢            O                                              Reaction        ⁢                                  ⁢        1            
That is, electrons released from the anode 1 travel through the external circuit and generate electric current, thereby implementing the function of a cell. Such a fuel cell 10 has advantages in that it can generate electricity by being operated in a low-noise, no-vibration manner or the like, without emitting air-polluting materials, such as SOx, NOx or the like, and CO2.
Meanwhile, fuel cells are classified into a diversity of types including Phosphoric Acid Fuel Cells (PAFCs), Alkaline Fuel Cells (AFCs), Polymer Electrolyte Membrane Fuel Cells (PEMFCs), Direct Methanol Fuel Cells (DMFCs), Solid Oxide Fuel Cells (SOFCs) and the like. The SOFCs are able to implement high efficiency power generation and combined power generation using e.g. coal gas-fuel cell-gas turbine or the like, and are suitable for small and large power plants or a decentralized power source because they are of a diversity of capabilities of power generation. Thus, SOFCs are an essential power generation technology for our introduction into the hydrogen-based economy and society of the future.
However, in order for the SOFCs to be commercialized, there is a problem to be solved in the processes of current-collection and manifold connection.
In the prior art, the current-collection was performed by the construction in which a metal form is provided in a cell and a metal wire is provided outside the cell. In the construction, there was a problem in that, as a cell is made larger, the amount of an expensive metal wire required and therefore the manufacturing cost are increased and the structure becomes complex, and mass production thereof is difficult to implement. Further, if a problem occurs in a cell and the cell has to be replaced with a new one, all of metal form and metal wire should be removed and the new metal form and metal wire have to be installed again in the cell, which is a problematic and complex process.
Another problem exists in the connection between a manifold and a cell. The manifold supplying hydrogen or air to the cell is in general composed of metal, whereas the cell is composed of ceramic. Thus, in order to combine heterogeneous metal and ceramic with each other, a brazing process is conventionally used. However, the brazing process has a problem in that depending upon a rate of increasing voltage applied to an induction coil, duration time of voltage applied, and a cooling condition after brazing, a clogging in the cell or weld defects may occur.